1. Field
The present invention relates to medical methods and devices, and, more specifically, to methods and devices for percutaneously implanting a valve.
2. Description of the Related Art
The circulatory system is a closed loop bed of arterial and venous vessels supplying oxygen and nutrients to the body extremities through capillary beds. The driver of the system is the heart providing correct pressures to the circulatory system and regulating flow volumes as the body demands. Deoxygenated blood enters heart first through the right atrium and is allowed to the right ventricle through the tricuspid valve. Once in the right ventricle, the heart delivers this blood through the pulmonary valve and to the lungs for a gaseous exchange of oxygen. The circulatory pressures carry this blood back to the heart via the pulmonary veins and into the left atrium. Filling of the left atrium occurs as the mitral valve opens allowing blood to be drawn into the left ventricle for expulsion through the aortic valve and on to the body extremities. When the heart fails to continuously produce normal flow and pressures, a disease commonly referred to as heart failure occurs.
The four valves of the heart (i.e., the tricuspid, the pulmonary valve, the mitral valve and the aortic valve) function to ensure that blood flows in only one direction through the heart. The valves are made of thin flaps of tissue that open and close as the heart contracts. Valvular heart disease is any disease process involving one or more of the valves of the heart. For example, disease and age can cause the tissue of a heart valve to thicken and harden, which can case the valve to fail to open properly and interfere with blood flow. This thickening process is often called stenosis. A heart valve can also become weakened or stretched such it no longer closes properly, which can cause blood leak back through the valve. This leakage through the valve is often called regurgitation. Problems with a heart valve can increase the amount of work performed by the heart. The increase in work can cause the heart muscle to enlarge or thicken to make up for the extra workload.
The standard treatment for replacing an improperly working valve is to replace it. Traditionally, valve replacement has been accomplished via an open surgical procedure. More recently, transcatheter valve replacement has been attempted via percutaneous method such as a catheterization or delivery mechanism utilizing the vasculature pathways. Open surgical procedures often include the sewing of a new valve to the existing tissue structure for securement. Access to these sites generally include a thoracotomy or a sternotomy for the patient and include a great deal of recovery time. Such open-heart surgical procedures can include placing the patient on heart bypass to continue blood flow to vital organs such as the brain during the surgery. Although open heart surgical valve repair and replacement can successfully treat many patients with valvular insufficiency, techniques currently in use are attended by significant morbidity and mortality due to the inherent invasiveness of open heart surgery.
According to recent estimates, more than 79,000 patients are diagnosed with aortic and mitral valve disease in U.S. hospitals each year. More than 49,000 mitral valve or aortic valve replacement procedures are performed annually in the U.S., along with a significant number of heart valve repair procedures. Since surgical techniques are highly invasive, the need for a less invasive method of heart valve replacement has long been recognized. As noted above, transcatheter heart valve systems have recently been developed in which heart valves are delivered through the heart by an intravascular catheter. Such transcatheter heart valves have the potential to reduce the anticipated mortality and morbidity rates associated with traditional surgical valve surgery particularly among patients of advanced age and/or with comorbidities. However, a need remains for improvements over the basic concept of transcatheter heart valve replacement. For example, current transcatheter valve replacement can sometimes result in vascular complications such as aortic dissection, access site or access related vascular and/or distal embolization from a vascular source. One method for reducing such complications is to reduce ratio of the diameter of the delivery device for the heart valve.